1. Field of the Invention
This invention is in the field of internal combustion engines and particularly the field of internal combustion engines burning solid fuels alone or in combination with liquid or gaseous fuels.
2. Description of the Prior Art
Prior art examples of char burning engines are described in the following U.S. Patents issued to applicant:
U.S. Pat. No. 4,372,256, Feb. 8, 1983
U.S. Pat. No. 4,412,511, Nov. 1, 1983
U.S. Pat. No. 4,698,069, Oct. 6, 1987
U.S. Pat. No. 4,794,729, Jan. 3, 1989
Char burning engines are described in these patents wherein char fuel, contained within a char fuel reaction chamber, is cyclically compressed with air followed by expansion of the product gases resulting from reaction of char fuel with compressed air. Most char fuels will react appreciably with the oxygen gas in the compressed air only when at a sufficiently high temperature, of the order of 900.degree. F. to 1000.degree. F., and will react rapidly with the oxygen gas in the compressed air only when at a higher temperature, of the order of 1200.degree. F. to 1800.degree. F.
Examples of char burning engines are described in general in U.S. Pat. No. 4,412,511, column 7, line 21 through column 11, line 45, and this material is incorporated herein by reference thereto. Such char burning engines comprise a char fuel reaction chamber into which char fuel is placed by a refuel mechanism via a refuel end and from which ashes are removed by an ash removal mechanism via an ash removal end and the char fuel reacts with oxygen in adjacent compressed gases within this char fuel reaction chamber.
The terms, internal combustion engine, and, internal combustion engine mechanism, are used herein and in the claims as defined in U.S. Pat. No. 4,412,511, column 1, line 65 through column 2, line 45, and this material is incorporated herein by reference thereto.
In some internal combustion engine mechanisms a reciprocating piston is operated within a cylinder as a combined means for compressing and expanding the gases, and the space enclosed by the piston crown and the cylinder walls is frequently also a reaction chamber wherein secondary reactions may occur during expansion. In this case the volume of this secondary reaction chamber varies cyclically and is a portion of the combined means for cyclically compressing and expanding gases. For multicylinder internal combustion mechanisms several combined means for compressing and expanding are joined together.
When such combined means for compressing and expanding the gases are used, each compression process occurs over a compression time interval during which the variable volume chamber decreases in volume and this is immediately followed by an expansion process occurring over an expansion time interval during which the variable volume chamber increases in volume.
For piston and cylinder mechanisms a crank and connecting rod, or equivalent mechanism, is used as a drive means for driving the internal combustion engine mechanism and the combined compressing and expanding means portion thereof through repeated cycles of compression followed by expansion. Various kinds of drive means and variable volume chamber means for compressing and expanding gases can be used such as the Wankel mechanism and the free piston mechanism as described, for example, in U.S. Pat. No. 4,372,256.
The term, oxygen gas, is used herein and in the claims as defined in U.S. Pat. No. 4,509,957, column 3, line 1 through line 8, and this material is incorporated herein by reference thereto.
The term, char fuel, is used herein and in the claims as defined in U.S. Pat. No. 4,412,511, column 2, line 46 through line 66, and this material is incorporated herein by reference thereto.
The term, changeable gas flow connection, is used herein and in the claims to means gas flow passages which can be opened or closed while the engine is running. The term, fixed open gas flow connection is used herein and in the claims to mean gas flow passages which remain open whenever the engine is running.
In many types of char burning engines combustion occurs in two steps: a primary reaction between the char fuel mass within the primary reaction chamber and oxygen in the primary air mass compressed into the primary reaction chamber during each compression process; and a following secondary reaction between the primary reaction products, emerging from the primary reactor during expansion, and oxygen in the secondary air mass retained in the secondary reaction chamber which may be the variable volume portion of the combined means for compressing and expanding. In one preferred form of char burning engine the primary reaction chamber is contained within a pressure vessel container which is separate from the combined means for compressing and expanding. This separate pressure vessel container must be cooled to prevent excess temperature rise and consequent weakening of the pressure vessel container walls due to transfer of heat from the primary reaction within the char fuel mass. But such cooling of the primary reactor pressure vessel container necessarily increases the rate of heat transfer out of the char fuel mass within the primary reactor. In this way some portions of the char fuel mass within the primary reactor may become cooled below their rapid reaction temperature. These cooled portions of char fuel may then not be completely reacted before removal and the fuel efficiency of the engine is reduced in consequence. It would be desirable to have a means for reducing the rate of heat transfer out of the char fuel mass which did not also increase unduly the temperature of the pressure vessel container.
Fresh char fuel and the primary air mass enter the primary reactor initially much colder than the existing char fuel mass undergoing primary reaction at its rapid reaction temperature and in this way act also to cool the char fuel mass. It would be further desirable to have a means for preheating the primary air mass and also the fresh char fuel being added into the primary reactor.